Resecch
Supported boy
Alabamna
So ybI)e an lb1 ndjwers
A Summuricry of 1982 lleauJlh
Alabcirnc Agr~cultural ExperiiwntSkilion
Auburn University
Gale A. Buchaiwin, Dimclor
Aubuirn, Alcibamc'

Auburn Univer ity
Auburn University, Alabama 36849
Alabama Agricultural Experiment Slation
Office of the Dean and Director Telephone (205) 826-4840
107 Comer Hall 
ACTS: 923-4840
September 7, 1983
TO: Alabama Soybean Check-Off Contributors
Attached are brief summary reports on 1982 research
provided by project leaders involved in soybean research
supported by the Alabama Soybean Producers. The findings
reported in these summaries illustrate the value of these
supported projects to the overall soybean research program
of the Alabama Agricultural Experiment Station.
We appreciate very much the support of our research
programs provided by the Alabama Soybean Producers. 
We
feel that the results of our research efforts are important
and enable our soybean industry to be more competitive.
We are firmly convinced that there are still many problems
that remain unsolved at this time. We pledge to you our
continued efforts in solving those problems that will
enable soybean producers to be as competitive as they
possibly can in the years ahead.
Sincerely yours,
Gale A. Buchanan
Dean and Director, AAES
A LAND-GRANT UNIVERS TY

SOYBEAN BREEDING AND GENETICS RESEARCHI
D. B. Weaver, Department of Agronomy and Soils
The first full year of the soybean breeding and genetics
program at Auburn was completed in 1982. From the F seed
obtained from the University of Georgia and planted in 1981,
2600 F
6 
lines were planted in the field at Tallassee in 6--foot
rows and evaluated for agronomic characteristics except for
yield. Most were maturity group VI or VIIo About 200 lines
were selected for further evaluation based on uniformity,
lodging resistance, and visual appearance, F1 hybrid seed
from crosses made in 1981 were advanced to the F
2 
in Belize,
Central America, during the winter of 1982. F
2 
plants were
planted at Tall:assee during the summer of 1982 and single
seed were harvested for further advancement during the 1983
winter in Belize. Crosses were made in the field between
parents having desirable characteristics and F
1 
seed were
sent to Belize for generation advance. Cross-pollination
conditions were excellent during 1982 and high numbers of
F
1 
seed were obtained.
Seven commercial and public cultivars were evaluated for
resistance to root-knot nematode (Meloidogyne .,tcognia0) in
an infested field during 1982. All cultivars were planted
with and without Soilbrom 90 (a nematicide) in a 2 x 7
factorial experiment. The major purpose was to evaluate the
interaction between cultivars and nematicide treatment. No
definite conclusion can be drawn until the experiment can
be repeated at least one more year, but it appeared that
public cultivars had higher levels of nematode resistance
than commercial cultivars. In the same field, 32 SI families
from a population that had been random-mated for six
generations were evaluated for root-knot nematode resistance.
Fifteen families were selected as resistant and these will
berandom-mated in 1983 as part of an ongoing recurrent
selection scheme aimed at improving overall levels of
nematode resistance. With the help of the winter nursery,
it should be possible to have a selection cycle every 2 years
0
Indeterminate and determinate cultivars (Duocrop and
Braxton and Foster, respectively) were evaluated 
for their
response to 100% defoliation at three growth stages in a
double-crop situation. Plants were planted after wheat on
June 21 and defoliated at the R4, R5, and R6 growth stages.
Based on one year's data, it appears that critical stages
for yield loss from defoliation are not the same as those
previously described for full season soybeans. The indeter-
minate growth habit proved to be no advantage in recovering
from the defoliation treatment as it has been in experiments
on full season soybeans
0  
Duocrop was significantly lower-
yielding than the best determinate cultivar, Braxton, in
the untreated plots, indicating that the indeterminate
growth habit is not an advantage in late planted soybeans.
Thirty cultivars were tested for reaction to stem canker
in a stem canker infested area near Marion Junction
0  
They
were visually rated for disease severity and compared for
two planting dateso There was a good correlation between
final seed yield and visual rating. Tracy M and Braxton
showed good resistance, and Hutton and Wilstar 790 were
most susceptible. Mean yield of the second planting date
was higher, but the increase in yield was due to better
performance of the susceptible cultivars. Later planting
had no effect on the resistant cultivars.
Fifty cultivars, experimental lines, and obsolete
cultivars were screened in replicated plots in 1982 for
genetic differences in physiological characteristics
related to midday plant water status. The purpose 
is to
find rapidly measurable characteristics which 
can be
used to screen segregating populations for 
yield potential.
Significant differences were observed within maturity
groups on several days for stomatal aperture, 
stomatal
resistance, leaf temhiperature, leaf photosynthetic 
rate,
and seed yield. Some of these characteristics were
correlated at certain growth stages, and correlations
with seed yield were high on days of high temperature 
and
light intensity.
SOYBEAN WEED CONTROL
R. Harold Walker, Department of Agronomy and Soils
Experiments were conducted at eight different
experiment stations in Alabama. Number of experiments at
each location were: Black Belt 5; Eo Vo Smith 3; Gulf Coast
4; Plant Breeding Unit 1; Prattville Field 3; Sand Mountain
3; Tennessee Valley II; Wiregrass 10. The general areas of
research were: (1) herbicide evaluation; (2) weed control
systems and economics; (3) pest management pesticide
interactions; 4) weed competition.
Herbicide Evaluation. Approximately 14 new compounds
were evaluated for weed control potential in soybeans. Of
these, only a few looked promising
0  
Dupont's A5969 at rates
of 15 to 140 grams per atre provided excellent control of
common cocklebur, sicklepod, bristly starbur, and prickly
sida. These weeds were controlled when A5969 was applied
preplant incorporated, preemergence, and postemergence over-
the-top. Soybean tolerance was good to excellent. This new
family of herbicides appears to offer excellent broad
spectrum weed control at extremely low rates. 
However, some
con'cern exists about potential carry-over to corn, sorghum,
and cotton. Research with this family of herbicides will
be expanded during 19830
The postemergence applied grass 
control herbicides,
Poast and Fusilade, continue to provide good to excellent
control of annual grasses and johnsongrass. Other compounds
showing equal or better grass control during 1982 were Dow's
XRM-4570 and American Hoerst's HOE-00581o Mixing Poast with
Basagran or Blazer again reduced the activity of Poast on
crabgrass. Combining Fusilade and Basagran was not as
antagonistic as combining Fusilade with Blazer.
One additional compound showing good weed control was
American Hoerst's HOE-00661, a paraquat-like herbicide. It
provided knock-down weed control as good as paraquat on most
6
species and better for smartweed and lambsquarters
controlo
Weed Control Systems and Economics. Weed control
systems research involves sicklepod, sicklepod plus morning-
glories, cocklebur, and johnsongrass. In addition to
collecting weed control and soybean yield data, we are
further evaluating each system by calculating net returns
to land and management (NRLM). This additional evaluation,
in general, shows we cannot afford or do not need 90% or
better weed control to produce high NRLMo I am convinced
this type information will help simplify our weed control
decisions. I am presently summarizing the sicklepod and
cocklebur data and will have it finished by spring 1984.
Pest Management/Pesticide Interactions. Research
was conducted during 1981 and 1982 to evaluate potential
pesticide interactions with preplant (Treflan, -encor,
Vernam) and postemergence (Blazer, Blazer plus 2,4-DB)
applied herbicides and insecticide/nematicide (Temik,
Nemacur) applied in all possible combinations. For both
years, no pesticide interactions 
were detected.
Research was conducted to evaluate what effects
toxaphene applied for sicklepod control had on soybean
insects and yield
0 
Treatments receiving toxaphene
produced yields just as good as treatments receiving no
toxaphene. However, where toxaphene was applied corn
earworm and three cornered alfalfa hopper populations
increased. This increase in harmful insects was not
found to affect soybean yield. We were able to document
again that beneficial insects were more numerous in
plots that had some sicklepod when-compared to those
kept weed-free all season.
Weed Compettiion. Weed competition is presently
being studied with sicklepod and cocklebur, the purpose
of which is to determine the relative competitiveness of
weeds as affected by soybean row spacing. Learning the
relative competitiveness of weeds under different
production systems should provide information that could
be used to Dredict yield losses when a mixed population
of weeds existsin a soybean field. The overall objective
is to develop better ways of deciding when or when not to
implement weed control,
Other competitive work is being done with bristly
starbur. This weed is very competitive with soybeans.
It is nearly as competitive 
as cocklebur. The bristly
starbur research will be completed during 1983.
SOYBEAN DISEASE RESEARCH
P. A. Backman, Department of Botany, Plant Pathology,
and Microbiology
Research on soybean diseases addressed two major
problem areas during the 1982 season: (1) developing
information on disease control assuming $6-7 per bushel
soybeans, and (2) developing control strategies for the
emerging stem canker problem before it spreads to the rest
of the state.
Improved Economies in Soybean Disease Control Programs.
Scheduling of soybean fungicide applications has been
evaluated since 1977, Sprays applied on an as-needed basis
were compared for profitability to the standard two-spray
system. The average number of sprays was reduced to 1.3 per
year, with $3 more soybeans produced per dollar invested
in fungicides. The standard program only returned $1.17
per dollar invested. These data have convinced duPont to
market Benlate in the Southeast based on an as-needed
application schedule.
Continuing studies indicate that the addition of
petroleum oil-surfactant blends to soybean fungicides
8
improves disease control in dry years, however, 
they do
not have the same effect in a wet year. Similar disease
control effects exhibited by the insecticide Lannate were
not present in the very wet summer of 1982.
Variability of the fungicide Bravo in controlling
soybean diseases has been a point of continuing mystery.
Results from this year indicate that the soybean
variety may affect'the performance of this fungicide.
This information is supported by results from potato tests
conducted in the Northeast. The ability to get
reproducible results from Bravo would give farmers an
alternative to the resistance-prone benzimidazoles.
Stem Canker. This disease continues to spread out
of the Black Belt and into adjacent areas and nearby
states. Resistant varieties and tolerant varieties have
been identified, as have those varieties that are highly
susceptible. The following points have been developed
that should aid farmers in developing a control strategy:
1. Plant the most resistant variety suitable for
your location, nematode analysis, and scheduling
requi rements.
2. Plant susceptible varieties last, so they will
avoid some of the disease.
30 Plant clean seed from clean areas, and if there
is any question have the seed treated.
4o Cultivation makes little difference in disease
severity.
5. Benlate applied in the month before bloom and
during pod elongation can greatly reduce disease.
60 In dry years, add some penetrator or similar
adjuvant to your spray tank.
7. Disease is more severe during drought or nematode
stress.
8o It is better to have more sprays or a low rate of
fungicide than less applications of a full rate.
SOYBEAN NEMATOLOGY RESEARCH
R. Rodriguez-Kabana, Department of Botany, Plant
Pathology, and Microbiology
Research in 1982 was directed to acquire data to
establish the relation between yield losses and nematode
numbers. Results indicated that the relation between yield
losses and nematode numbers is affected by the cultivar and
that there may also be a seasonal effect, It was possible
to establish equations to describe the relation between
yields and root-knot nematode (Meologyne incognitd)
numbers for cultivars: Ransom (susceptible), Bragg
(intermediate tolerance), and Foster 
(tolerant)
0 
Generally,
the linear equations for resistant cultivars have slope
values smaller than those for. susceptible varieties; however,
the yields corresponding to the no-nematode (clean field)
situation indicated that many varieties are superior in
yield potential to the tolerant varieties.
These results represent a first step in the development
of accurate recommendations for management of nematode
problems in producers' fields. Once the relation between
yield losses and nematode numbers is established, then
we can put dollar values to it and come out with
recommendations that will be more accurate than those we
have today.
Other research involved determination of the efficacy
of combination systemic + fumigant nematicides. Results
indicated no economic advantage from the use of combination
treatments. The fumigant nematicide (ethylene dibromide)
was much more economical alone and no yield advantage was
gained by including Nemacur, Furadan, Temik, or Vydate
with it.
Other soybean research was directed to isolating fungi
parasitic of nematodes. A number of fungal species capable
10
of destroying eggs of soybean cyst and root-knot
nematodes were isolated from soybean fields. Some of
these species offer good potential for development 
as
biological control agents. However, this will take
somne time before we can move .with it in the field.
Cooperative work with Dr. David Weaver revealed
that there were no commercially available cultivars
among those tested that could be grown economically
in a field severely infested with the root-knot 
nematode
(Mo i(co9gni:a) without 
the use of an efficacious 
nematicide.
There was a total of 2,990 field 
plots dedicated to
soybean research on nematode control in 1982.
Future Plans. We plan to continue work on
determination of yield loss equations and to expand work
on population dynamics of root-knot and cyst nematodes as
influenced by cultivar and season. This 
is absolutely
necessary to acquire a body of knowledge for extension
personnel to be able to make accurate nematode control
recommendations. It is visualized that this work will
require several years.
We plan to continue cooperative work with Dr. David
Weaver on development of nematode-resistant varieties,
We also will continue nematicide screening work and
experiments on ways and methods of applying these materials
in the most efficacious manner.
Work on biological control and the effect of rotations
will continue. We are planning development of new rotation
systems with innovative crops. This work will be done in
cooperation with Drs. Harold Walker and Joe Touchton.
11
MANAGEMENT OF SOYBEAN INSECT PESTS
T. P. Mack, Department of Zoology-Entomology
The effects of three cornered alfalfa hoppers on soybean
plant growth were investigated this past summer in an
experiment conducted at the Auburn University Rhizotron.
Plants were infested with 16 three cornered alfalfa hoppers
per row-foot in one side of a caged bin, with control
plants on the other. side of each bin. Four bins (replicates)
were run. All plants were kept relatively insect free until
the R1 stage, when the bins were infested. Soybean root
growth measurements were made twice weekly. No significant
differences (P=.05) occurred in soybean root growth between
infested and control plants. However, three cornered
alfalfa hopper feeding significantly reduced stem, pods,
and seed dry weight. There was a 48% yield loss in
infested plants compared to uninfested plants. This work
will be continued in 1983 with an early season infestation
being examined.
Toxaphene applications in soybeans for sicklepod
control affected the population dynamics of a number of
insects. It increased podworm density with both broadcast
and band applications kept weed free all season. However,
there were no differences in podworm populations between
toxaphene sprayed or nonsprayed plots kept weed free for
only 2 or 6 weeks. This appears to be due to increased
numbers of natural enemies in plots kept weed free for 2
or 6 weeks and receiving toxaphene compared to plots kept
weed free all season and 'reciving no toxaphene. 
Thus, the
occurrence of some sicklepod apparently increased the
abundance of natural enemies. Three cornered alfalfa
hopper populations also increased in the toxaphene sprayed
plots. The increases in abundance of these two important
soybean insect pests were due, we believe, to decreases
in the natural enemy populations from the toxaphene
applications. GeocoALui pu.nctipe immatures and Striped
Lynx spiders, which are common natural enemies, greatly
12
decreased in abundance in the 
toxaphene sprayed plots.
However, insect fluxes were not found to affect soybean
yield, A second year's data will be collected to verify
our first year's results.
Temperature and age of the 
adult female definitely
affected the oviposition rate of soybean loopers.
Approximately twice as many eggs were laid at 26
0
C than at
the coolest temperature tested (17
0
C). Further, adult
female soybean loopers laid eggs at their fastest rate at
260C. The longevity of adult female soybean loopers
decreased linearly as temperature increased. The daily
oviposition rate was found to be significantly related
to temperature and adult age in a regression model. With
this model it is now possible to estimate the number of
eggs laid by a female soybean looper given her age and the
temperature. This can then be related to the number of
adult female loopers present in a field to determine
when an outbreak of loopers is likely to occur and its
approximate size.
Sixty soybean strains, cultivars, 
and varieties were
monitored weekly in a replicated test designed to
determine if any of the plants.were resistant to any of
the commonly occurring soybean insect pests. A number of
the strains showed some resistance to soybean loopers and
three cornered alfalfa hoppers, as measured by number of
loopers per row-foot. This work will be continued in 1983.
Four insecticide efficacy tests were conducted this
past year. These looked at both systemic and foliar
applications of a number of different compounds, and their
efficacy against podworms, soybean loopers, bean leaf
beetle, and three cornered alfalfa hoppers. Compounds
Uested include a number of experimental synthetic
pyrethroids, a fungicide (screening for insecticidal
activity), and an insect growth regulator. A number of
the unregistered compounds showed great promise for
controlling soybean loopers, and 
all of the new compounds
controlled podworms and three cornered alfalfa hoppers.

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